1. Field of the Invention
The present invention relates to a novel method and apparatus that permits application of fertilizer below seed at the time of seeding with a minimum of soil disturbance.
2. Description of the Art
The precise placement of fertilizer and seed is critical for the efficient use of fertilizer and for enhanced plant growth especially in conservation tillage systems which have crop residue on or near the soil surface. Fertilizer placed on or near the surface gets tied up in the decomposition of crop residue and therefore is not available for the young plants. Fertilizer placed in high concentrations next to the seeds can result in toxic effects to the seedlings. For example, if the concentration of fertilizer is too high close to the developing seedling, germination and emergence can be depressed. This toxic effect of fertilizer is greatest for hot and dry seedbeds such as encountered in early fall planting in summer fallowed systems.
Klepper et al., in the Journal of Soil and Water Conservation, Vol. 38, pp. 250-252 (1983), describe the optimum placement of fertilizer for cereal grain production on silt loam soil as 3 to 5 cm below the seed or 3 cm below and up to 5 cm to one side. Factors such as soil water content, soil temperature, proximity of the fertilizer to plant roots, and type and concentration of fertilizer influence the fertilizer toxicity problem to young seedlings.
Placement of fertilizer at the time of seeding is recognized as an important means to improve crop production and reduce the number of field operations. Present planting devices that place fertilizer at seeding time are of two types, those that use separate soil engaging tools for placement of seed and fertilizer and those that use a single soil engaging tool to place both fertilizer and seed. The devices that have separate soil engaging tools are not suited to soil and water conservation production systems that leave crop residue on the soil surface to reduce the volume and velocity of water runoff. Separate soil engaging tools for seed and fertilizer bury more crop residue and crop residue becomes tangled in the openers more easily than with a single soil engaging tool for placement of seed and fertilizer.
Known devices for placement of seed and fertilizer through one soil engaging tool include U.S. Pat. No. 3,908,567; U.S. Pat. No. 4,388,878; U.S Pat. No. 3,797,418; U.S. Pat. No. 4,278,036; U.S. Pat. No. 4,417,530, and U.S. Pat. No. 4,565,141.
U.S. Pat. No. 3,908,567 shows an apparatus which includes a plurality of chisel-shaped applicator knives to which dry fertilizer or seeds are fed. Liquid ammonia is fed to a conduit behind each knife and directed onto a ribbon of the dry particulate matter deposited at the bottom of each channel formed by the knives. This apparatus does not provide means for placing fertilizer an adequate distance from the seed and therefore there is a high potential for fertilizer toxicity problems to the germinating seed especially from the ammonia gas used to help discharge the particulate matter.
U.S. Pat. No. 3,797,418 shows a minimum tillage planter which includes a forward-oriented disk coulter, a delta-wing-shaped seed opener, and a fertilizer opener contiguously mounted aft of the seed opener having wing-like members forming planar continuations of the wing portions of the seed opener. This planter does not provide means for placing fertilizer below the seed where the developing plant roots will have ready access to the fertilizer.
U.S. Pat. No. 4,388,878 discloses a seeder foot assembly which includes a furrow opening body portion and a plurality of feed tubes located behind, one above the other, for discharging materials such as seed, fertilizer, and herbicides into the soil. U.S. Pat. No. 4,278,036 shows a rotary tiller slot planter which includes a subsoil shank which forms an initial trench and includes a fertilizer tube for depositing fertilizer in the trench, and a seed tube shank including a seed tube and insecticide tube therein for depositing seed and insecticide above the fertilizer. The main disadvantage of these devices is that they cause excessive soil disturbance during placement of fertilizer and seed.
U.S. Pat. No. 4,417,530 and U.S. Pat. No. 4,565,141 show planting devices which include a chisel type furrow opener and a shank having a first delivery tube for delivery of fertilizer and a second delivery tube behind the first tube for delivery of seed behind and above the fertilizer. U.S. Pat. No. 4,565,141 further includes a seed bed packing plate for covering the fertilizer with soil prior to seeding. These devices are not suitable for seeding into soil conditions that have dry soil in the top 5 to 10 cm and crop residue on the surface for erosion control. Excessive amounts of soil are disturbed in order to place the fertilizer below the seed and have the seed in contact with soil sufficiently moist to germinate the seed and produce seedling emergence. The excessive soil disturbance results in reducing valuable crop residue on the soil surface, leaving the soil surface rough and promoting loss of soil water from the seed zone.
Wilkins et al. (1981 Research Report - Columbia Basin Agricultural Research Special Report 623, pp. 51-55) describe a USDA modified deep furrow opener to simultaneously place seed and fertilizer in the soil with the fertilizer below the seed. This opener includes a shank for attachment to a grain drill, an opener attached to the front of the shank for opening a furrow, a fertilizer tube extending through the shank for feeding fertilizer into the furrow, and means for directing seed into the soil at a distance behind and above the fertilizer. The primary disadvantage of this opener is that it causes a large volume of soil to be disturbed during placement of fertilizer and seed, resulting in the creation of high ridges adjacent to seed rows. This contributes to increased soil erosion, reduction of valuable crop residue at the surface, increase in loss of soil water, and creation of a rough soil surface.